Dampening roll cover and fabric therefor



y 13, 1965 w. J. KENNEDY, JR 3,183,578

DAMPENING ROLL COVER AND FABRIC THEREFOR Filed Sept. 26, 1962 United States Patent 3,183,578 DAWENING ROLL CQVER AND FABRIC THEREFGR William I. Kennedy, Ira, Wrentham, Mass., assignor to The Kendall Company, Boston, Mass, a corporation of Massachusetts Filed Sept. 26, E62, Ser. No. 226,386 13 Qlaims. (Cl. 29-120) This invention relates to dampening roll covers. More particularly it relates to a disposable dampening roll cover comprising a non-woven fabric of enhanced waterholding properties.

Such covers are widely used in lithographic offset printing devices, where their function is to transfer moisture to a lithographic plate to maintain a certain Waterink balance suitable for printing. Such devices, of varying degrees of complexity and varying numbers of rollers, are well known in the art, and need be described no further here.

conventionally, dampening rolls in lithographic presses consist of a rubber-covered roll with an outer sleeve of molleton, a thick type of flannel. The molleton may be supplied to the roll in the form of a sewn tubular sleeve, or it may be adhesively fixed to the roll, in One piece, employing a butt joint. Alternatively, instead of being formed into a tubular sleeve, the molleton may be slit into strips and spirally wound onto the surface of the rubber-covered roll, being fixed thereto by means of an adhesive or by the use of double-faced adhesive tape. When the roll surface becomes soiled with usage, it must be replaced, which is a time-consuming and intricate operation customarily performed by an outside service possessing special equipment designed for this function.

It has also been proposed to provide dampening rolls of a disposable type, wherein a fabric of molleton, velvet, or pile fabric is used to cover a hollow, more or less rigid shell, as disclosed in US. Patent 2,966,724, of Ianuary 3, 1961, to Morris C. Swope.

I have found that an improved type of disposable dampening roll cover may be devised by the provision of a water-resistant cardboard core of approximately onequarter inch in shell thickness with a covering of a special type of non-woven fabric, described more fully hereinbelow. Such precovered tubes may be made in a range of standard sizes, and are preferably supplied with a set of end-flanges serving to facilitate centering the covered shell on a dampening roll, the surface of which needs renewing. Such flanges are known in the art and do not constitute a part of this invention.

The invention will be more clearly understood from the accompanying drawings, in which:

FIGURE 1 is a perspective view of the covered tube of this invention, partly broken away, and showing one centering end-flange 12 in place.

FIGURE 2 is a perspective view of the method of Wrapping the nOn-woven cover 16 onto the shell 14.

FIGURE 3 is a cross-sectional view, greatly enlarged, of the mixed-fiber web used to produce the non-Woven fabric cover.

FIGURE 4 is a cross-sectional view, also greatly enlarged, of the web of FIGURE 3 after it has been needled and shrunk into finished non-Woven form and prior to being applied to the shell surface.

A satisfactory cover for a dampening roll must meet several important requirements. It must be highly absorbent and readily absorbent, so that it will not only carry and transfer a film of water to a lithographic plate, but it should wet out readily from a dry state when operations are begun again after a shut-down period. The roll cover should have a smooth, continuous surface so "ice that the applied water film will be uniform. It should be of such a nature that it can be applied to the dampening roll without seams, ridges, or high points. It should be relatively free from lint, to allow the reproduction of a clear image, and it should resist the pick-up of lithographic inks, which are generally of an oleaginous nature.

Finally, an ideal dampening roll cover should possess a definite degree of resilience. As mentioned above, when conventional fabrics are wound onto a dampening roll, it is customary to have the outer surface of the roll made of rubber, to serve as a back-up cushion for the fabric and insure a smooth, even deposition of water. When fabrics are applied to a rigid hollow core, to create a disposable shell, this cushioning effect is lacking.

I have found that by the shinkage of a needled mixture of certain polyvinyl alcohol fibers and absorbent (preferably cellulosic) fibers, a non-woven fabric is provided which meets all the requirements, set forth above, which are needed in a dampening roll cover, and which performs in a highly efficient, durable, and economical manner.

Preferably, I blend together between 25% and of absorbent fibers, such as viscose rayon, with between 75% and 25% of polyvinyl alcohol fibers which have not been formalized or acetylated to reduce their natural tendency to swell in water to a substantially gel-like state.

In FIGURE 3 the viscose fibers are shown as the light fibers Ztl, and the polyvinyl alcohol fibers are more heavily traced, as at 18. This is for convenience in representation only, and does not mean that the polyvinyl alcohol fibers are necessarily heavier, or of coarser denier, than the viscose fibers.

I have found polyvinyl alcohol fibers of the type known generically as non-acetylated Vinylon to be satisfactory for my purposes. This fibrous blend is then passed through a card, garnett, air-lay machine or equivalent device to form a mixed fiber fleece of blended fibers, preferably in the range of 60 to grams per square yard. The fleece is then needled in a needle loom to provide an integrated, self-sustaining batt whereby at least a portion of the fibers of said batt are displaced in a direction normal to the plane of said batt, which is then passed through a hot water bath. In the hot bath process there is substantial shrinkage and fusing together of the polyvinyl alcohol fibers, resulting in area shrink and an increase in Weight to between 200 and 250 grams per square yard. The smooth-surfaced non-woven fabric at this stage is a dense felt of substantial thickness, as shown in FIGURE 4, and due to the fused nature of the polyvinyl alcohol fibers, it is essentially stiff and rigid. In this form it is slit into strips, conveniently between one and three inches in width, after which it is wound, for example, helically around and adhesively secured to a shell of appropriate size to form a disposable sleeve, premounted, which may be slid as a replacement cover ,over a dampening roll in a lithographic press, or centered on a shaft by means of flanges, with aminimum of adjustment and breaking in. In fact, as explained hereinbelow, the wet-out time, or running-in time of a roll of this sort, starting from a dry state, is remarkably short.

The following example will illustrate one specific embodiment of the invention. It is to be regarded as exemplary, and the inventon is not restricted thereto, since many equivalent variations will be apparent to those skilled in the art.

Example I A fibrous blend of 50% 3 denier 1%; inch staple absorbent viscose rayon fibers and 50% 1.4 denier 1% inch polyvinyl alcohol fibers of the type known as Vinal VP 101, a product of the Kurashiki Rayon Company, was passed through an air-lay device and collected on a conveyor belt as a fieece weighing 85 grams per square yard. The fleece was unified by passing it twice through a Hunter Model 9 needle loom, once on each face, at a rate of 2 yards per minute, thus effecting approximately 370 needling interlocking penetrations per square inch of material. The natural spreading tendency of the needling process gave a unified batt weighing about 70 grams per square yard.

This 70 grams needled batt was passed through a water bath warmed to 140, F., containing an optional 2% of propylene glycol to facilitate penetration and plasticization of the fibrous mass. Excess moisture was removed by the passage of the saturated batt through a squeeze nip loaded to 40 pounds pressure per inch of nip, after which the moistened batt was processed at a rate of 6 yards per minute over a set of -22 dry cans of 23 inches diameter, heated by steam at 100 pounds pressure, and for complete drying through a curing oven heated to 325 F. Shrinkage of the batt took place both on the dry cans, and to a lesser degree, in thefinal curing oven. Shrinkage was both lengthwise and widthwise, so that the needled batt entering the finishing process at 70 grams per square yard and a width of 70 inches emerged in final form at a width of 39 inches and a weight of 225 grams per square yard. In an isotropic batt of this sort, this represents about a 44% widthwise shrinkage and an equivalent lengthwise shrinkage, for an overall 69% area shrink.

Naturally, if the fibrous blend is processed through equipment which orients the fibers in a particular direction, or if the processing tensions are such that shrinkage in one direction is suppressed, the parameters of the process will differ from those set forth above. Since the unique behavior of my dampening roll cover appears to be a function of the interaction of a polyvinyl alcohol and a second, non-gelling fibrous mass, considerable deviation from the above operating conditions may be exercised without departing from the spirit of the present invention.

The relatively stiff and firm felted product from the above process is slit into strips 2% inches wide and is then helically wound on, for example, a multi-layered papercore, suitably water proofed, of 2% inches outside diameter and inch wall thickness, using an adhesive such as a mixture of equal pants of Hycar 1562X-l03, a

nitrile latex produced by B. F. Goodrich Chemical Company, and Vinsol resin emulsion produced by Hercules Powder Company.

I have found that although the dry product from thethick paper, it undergoes a drastic and remarkable change inproperties when wet out, as in normal usage as a dampening roll cover. a dry weight of 225. grams per square yard, and in a dip and drain test absorbs 750% of its weight in water. It has excellent grease resistance, due presumably to the very hydrophilic nature of the viscose rayon and the polyvinyl alcohol phase. Its solvent resistance is excellent except for boiling Water.

In the dry state the material has a tensile strength of 23 pounds per 2 inch widestrip and an elongation of 6% in the machine or long direction, with a strength of 17 pounds and an elongation of 8% in the transverse orteristic of my dampening roll cover when moist. In the shrinkage process set forth above, there isv apparently a profound swelling and fusing together of the polyvinyl alcohol fibers, which nevertheless apparently stops short of complete solution and dispersion of these fibers. The

The product of the above example has rayon fibers apparently serve as wicks to carry water into the polyvinyl alcohol phase, with which they are intimately associated. At' any rate, I have found that the cover of my invention has high capillarity, so that when water is applied to dampen the roll before operation of the press, there is, a rapid transition from a rigid, firm cover to a resilient, elastic cover which can best be described as rubbery. This rubbery, resilient, deformable character is very desirable in a dampening roll cover, particularly whencombined withsuch an afilnity for water as to allot-v a moisture retention of 750%, as set forth above.

Due to the bouncy resilience of my cover, no rubber underlay or back-up layer need be used, and my fabric may be wound directly onto a rigid shell or core. Moreover, the plastic nature of my cover when Wetmeans that the helical grooves of FIGURE;1, characteristic of helically wound coverings, substantially disappear when the roll is wet out and put into operation. .Even though my cover is adhesively united to the core, it displays enough plastic flow to allow a rapid evening outof the surface,

said absorbent fibers being dispersed through and in intimate contact with said polyvinyl alcohol fibers, at least a portion of said fibers being displaced in a plane normal to the palne of said nonwoven fabric.

2. The product of claim '1 wherein the polyvinyl alcohol fibers are coalesced by fusion into a ramified, substantially continuous phase, and the absorbent fibers are viscose rayon.

3. The product of claim 1 wherein the polyvinyl alcohol fibers comprise between 25% and 75 of the felted mixture and the absorbent fibers comprise between 75% and 25% of said felted mixture.

4. The product of claim 1 wherein the felted mixture is a needled felt.

5. The product of claim 1 wherein the felted mixture is a needled felt that has been subjected to a shrinkage of at least 40% in area.

6. A disposable dampening roll cover comprising a relatively rigid water-resistant cylindrical core adhesively united to a felted mixture of absorbent fibers and polyvinyl alcohol fibers, said polyvinyl alcohol fibers being fused together and said absorbent fibers being dispersed through and in intimate contact with said polyvinyl alcohol fibers;

7. The product of claim 6 wherein the polyvinyl alcohol fibers are coalesced by fusion into a ramified, substantially continuous phase, and the absorbent fibers are viscose rayon.

8. The product of claim 6 wherein the polyvinyl alco hol fibers comprise between 25% and 75% of the felted mixture and the absorbent fibers comprise between 75 and 25 of said felted mixture,

9. The product of claim 6 wherein the felted mixture is a needled felt.v

10. The product of claim 6 wherein the felted mixture is a needled felt that has been, subjected to a shrinkage of at least 40% in area.

11. The process of producing a disposable dampening roll cover which comprises felting a fieecy mixture of absorbent fibers and polyvinyl alcohol fibers, wetting the felted mixture, shrinking and drying the felted mixture 5 6 to form a relatively firm and rigid felt, slitting the firm References Cited by the Examiner and rigid felt into strips, spirally winding at least one of UNITED STATES PATENTS said strips onto a Water-resistant cylindrical core, and v securing said spirally-wound strip to said core. 2528129 10/50 Franc 161 80 12. The process of claim 11 wherein the fibrous mix- 5 2,545,700 3/51 MacKey 29120 X ture comprises between 25% and 75% polyvinyl alcohol 2962762 12/60 Hartman 156-34 fibers and between 75% and 25% absorbent fibers, and the Shrinkage is at least 40% in area WALTER A. SCHEEL, Przmary Exammer.

13. The process of claim 11 in which the spirally- J. D. BEIN, Examiner. wound slit felt is adhesively united to the water-resistant 10 cylindrical core. 

6. A DISPOSABLE DAMPENING ROLL COVER COMPRISING A RELATIVELY RIGID WATER-RESISTANT CYLINDRICAL CORE ADHESIVELY UNITED TO A FELTED MIXTURE OF ABSORBENT FIBERS AND POLYVINYL ALCOHOL FIBERS, SAID POLYVINYL ALCOHOL FIBERS BEING 